What are you feeling? For the first time, a brain scan might be able to answer that question.

It’s not exactly mind reading, but a new program can identify emotional states— from happiness to sadness, lust to disgust— simply by analyzing brain activity, according to a recent study.

The technique isn’t just a parlor game; since emotional disturbances lie at the center of most psychiatric problems, a reliable way to detect feelings from brain scans could help researchers to better understand what goes wrong in cases of depression, autism, schizophrenia, anxiety disorders and many other conditions, as well as offer new insight into how emotions work.

The brain images represent the first time that scientists can “find neural signatures of different emotions,” says Karim Kassam, they study’s lead author and assistant professor of social and decision sciences at Carnegie Mellon University.

The research, which was published in the journal PLoS One, involved 10 method acting students, mainly women, who were part of the the Carnegie Mellon Drama Community at that university in Pittsburgh. Method acting teaches students to embody the emotions of a character, fully immersing themselves in the experience by relying on personal feelings as a guide, so the scientists were confident that the students asked to display specific emotions would actually be feeling them.

Before having their brains scanned, the actors were asked to write scenarios so they could quickly evoke feelings generated by 18 words designating nine emotions: anger, disgust, fear, lust, happiness, pride, shame, envy and sadness. The actors also wrote a calm scenario that they used as a control when they were instructed not to act out intense feelings.

The volunteers were then placed in a scanner that recorded their brain activity as they saw the emotion-related words, flashed one at a time on a screen. After each appeared, each student had nine seconds to act out the emotion mentally, increasing its intensity over time. Afterward, they rated how deeply they had actually been able to feel the appropriate emotion. Each actor conducted multiple trials of each emotion.

To determine whether the acting differed substantially from actually feeling the emotion, the scientists also flashed 24 images, half of which were disgusting, the rest neutral, across the participants’ screens. The actors seemed to be pretty good at their method acting exercise, since their brains registered similar activity when viewing the disgusting images as when they were acting disgusted.

Based on the data collected on a particular actor’s brain activity, the scientists then developed an algorithm for predicting which patterns were related to which feelings. Around 84% of the time, the computer’s first guess as to what emotion was being displayed was correct, showing that individuals have predictable brain signatures for what they are feeling. These exact signatures may not be shared, however, since the program was less successful at predicting one person’s emotions by using data from other people’s scans. (It still performed better than chance, however, getting it right on the first time 71% of the time on average.) “Everyone feels like they understand anger, sadness or happiness and they think that they can define emotion, but it turns out to be very difficult to define and there’s not even a scientific consensus,” Kassam says.

What distinguished the varying feelings? Four factors emerged from the data. The most important involved whether the emotion was positive or negative. Positive valence made it highly unlikely that the computer would mistake happiness for shame or sadness for pride — indeed, those were the least likely mistakes it made. Arousal also played a role. “Sometimes we’re very energetic and sometimes we’re sluggish: anger looks very different from sadness on a dimension like arousal,” Kassam explains. An emotion’s social relevance also separated them — anger or envy, for instance, generally involves others while disgust is frequently more solitary.

Finally, the researchers say that lust appears to have a brain profile all its own, distinct from other emotions and therefore unlikely to be misread by the computer. “Lust looks like neither positive nor negative emotions,” Kassam says. The images showed that there were brain regions that were only activated by sexual desire. Why? Lust may stand out because of its critical role in reproduction — or because it can be either desirable or not, depending on the situation. For example, lust may be perfectly pleasant when experienced at home with one’s spouse— but excruciatingly embarrassing and uncomfortable in other settings, especially when directed at inappropriate targets.

“[The study] basically shows that the differences between the emotions seem to be driven by valence, arousal, and social factors, along with their interesting lust factor,” says Russell Poldrack, professor of psychology and neuroscience at the University of Austin in Texas, who was not associated with the work. “There is nothing new about this, but these results are a nice confirmation, given that they didn’t design the study to find those factors but they instead fell out of the data.”

The fact that emotions may have some predictable brain signatures may also offer insight into how these emotions are formulated and, potentially, how they might be altered in cases of disease. “[These results are] important because it hasn’t been possible yet to move toward brain predictions of what people are feeling,” says Tor Wager, associate professor of neuroscience at the University of Colorado in Boulder, who was not associated with the research. “It’s tremendously important for psychiatry because we have had not had markers for emotional processing and it is disturbed in virtually every psychiatric disorder and in some neurological diseases like Parkinson’s.”

Emotions are also critical for many basic cognitive functions that we don’t often association with feelings. Some experts argue, for example, that emotions are biological programs for decision making, evolved to guide animals to make the best choices for successful survival and reproduction. They note that even the most apparently “rational” choice involves emotion because making a “good” choice requires seeing one option as preferable and preference involves desire. (This may be why depressed people so often have difficulty taking action: if everything seems equally bleak, making a choice can become impossible.)

More research will be needed before the scans can be used to precisely answer questions like ‘How are you feeling?,’ but, if the results are confirmed and repeated, it may not be long before your brain gives your emotions away.